1. Field of the Invention
The present invention relates to exposure apparatuses, exposure methods, and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method which are used in a lithography process to produce electronic devices such as a semiconductor device and the like, and a device manufacturing method which uses the exposure apparatus or the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
Substrates such as a wafer, a glass plate or the like subject to exposure which are used in these types of exposure apparatuses are gradually (for example, in the case of a wafer, in every ten years) becoming larger. Although a 300-mm wafer which has a diameter of 300 mm is currently the mainstream, the coming of age of a 450 mm wafer which has a diameter of 450 mm looms near. When the transition to 450 mm wafers occurs, the number of dies (chips) output from a single wafer becomes double or more the number of chips from the current 300 mm wafer, which contributes to reducing the cost. In addition, it is expected that through efficient use of energy, water, and other resources, cost of all resource use will be reduced.
Meanwhile, when the size of the wafer becomes as large as 450 mm, while the number of dies (chips) output from a single wafer increases, the probability becomes high of throughput decreasing due to an increase in the time required to perform an exposure process on a single wafer. Therefore, as a method of suppressing the decrease in throughput as much as possible, employing a twin stage method (for example, refer to U.S. Pat. Nos. 6,590,634, 5,969,441, 6,208,407 and the like) can be considered where an exposure process on a wafer is performed on one wafer stage, and processing such as wafer exchange, alignment or the like is performed concurrently on another wafer stage. However, in the case a 450 mm wafer is subject to processing using an exposure apparatus of the conventional twin stage method without any changes, there was a risk that the throughput would not be improved sufficiently enough.
Semiconductor devices are gradually becoming finer, therefore, high resolution is required in exposure apparatuses. As means for improving the resolution, shortening a wavelength of an exposure light, as well as increasing (a higher NA) a numerical aperture of a projection optical system can be considered. To increase the substantial numerical aperture of the projection optical system as much as possible, liquid immersion exposure in which a wafer is exposed via a projection optical system and a liquid is effective.
As the local liquid immersion type exposure apparatus which employs the twin stage method, the exposure apparatus disclosed in, for example, U.S. Patent Application Publication No. 2008/0088843 is known. According to this exposure apparatus, improvement in resolution and throughput can be expected. However, in the local liquid immersion type exposure apparatus disclosed in U.S. Patent Application Publication No. 2008/0088843, a liquid immersion space formed under the projection optical system has to be constantly maintained so as to maximize the throughput, and in order to do so, a member of some kind has to constantly be placed interchangeably, right under the projection optical system. And, it is desirable for this interchangeable placement of the member to contribute to improving the throughput of the apparatus.